The present invention relates to a tiered storage system. More specifically, the invention relates to selection of blocks and pages for placement in the storage system.
A tiered storage system utilizes at least two types of storage devices in the form of computer equipment on which information can be stored. More specifically, a storage device is a hardware device used to record and store data files and objects. Forms of storage include, but are not limited to a solid state disk drive (SSD), and a hard disk drive (HDD). A SSD, also referred to as an electronic disk drive, is an electronic storage drive built on solid state architecture. More specifically, the SSD is built with flash memory to store non-volatile data and dynamic random access memory. The SSD is an entirely electronic storage device and its physical assembly contains no mechanical parts. The HDD employs a hard disk to storage data on a moving magnetically coated surface or surfaces.
The SSD is generally a faster and more expensive form of storage on a storage unit basis in comparison to the HDD. In a hierarchical organization of storage, different devices are placed in hierarchical tiers. For example, in a system with both a SSD and a HDD, the SSD is placed in one tier of the hierarchy, and the HDD is placed in a second tier of the hierarchy. Data is placed in a storage device in one of the tiers based on characteristics of the data, frequency of data access, and associated storage cost(s).